Libcinfo tsd tls refactor#10
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dalehamel
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dalehamel
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Co-authored-by: Mackenzie <mackenzie.jomard@datadoghq.com> Co-authored-by: Florian Lehner <florianl@users.noreply.github.com>
Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
…n-telemetry#950) Co-authored-by: Timo Teräs <timo.teras@iki.fi>
The DTV variables read from extracted __tls_get_addr can be used to read TLS variables. If this symbol is missing, empty introspection data is returned.
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Moving my upstreaming efforts from #7 here, to avoid adding the ruby stuff since that gets complicated.
What
Refactor's
tpbaseto belibcpackage, as it provides additional info about libc.In particular, this adds DTV introspection information and bundles this with the TSD info into a new
LibcInfo.Why
We need the DTV information to look up TLS variables when TLS descriptors are not available.
How
This adds disassembler code for extracting the DTV information from
__tls_get_addrif it is present in the libc.It should be supported for musl and glibc, on both x86_64 and aarch64, and test cases from different libc versions and architectures are added to validate that this is the case.
The
tpbasepackage is renamed tolibc, and related functions are renamed to be more generic, but otherwise the functionality is unchanged.Nothing actually uses the new DTV data yet, another PR will follow up to add that for Ruby which reads the execution context from a TLS variable.